Heterogeneous Catalysis Opportunities and challenges

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Heterogeneous CatalysisOpportunities and
challenges
J. K. Nørskov Center for Atomic-scale
Materials Physics Technical University of
Denmark norskov_at_fysik.dtu.dk

• Challenges
• Societal needs
• Developing the basic understanding
• Opportunities
• Designing at the nano-scale

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Challenges I
Dream reactions waiting for a catalyst
Jens Rostrup-Nielsen XVII Sympósio
Iberoamericano de Catálisis, July 16-21, 2000
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Challenges II

• Dreaming on .
• Heterogeneous catalysts for assymmetric synthesis
• Photolytic water splitting (hydrogen economy)
• Biomimetics, synthetic enzymes
• Non-thermal processes in general
• (e.g. electro- and photocatalysis)

See E. Derouane, CATTECH 5, 226 (2001)
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Challenges III

• The science of heterogeneous catalysis
• A comprehensive scientific basis
• Much has been done
• Much more is needed (oxides, size effects,
  photocatalysis, electrocatalysis, relation to
  homogeneous and enzyme catalysis )
• Making the insight useful!
• The ultimate test

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Opportunities- design at the nano-scale

• Rational catalyst design
• Discovery on the basis of insight
• Data-driven methods
• - Accelerated discovery by access to
• large amounts of data
• Bio-inspired catalysis

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Rational catalyst design

• What determines the catalytic
• activity/selectivity/lifetime ?
• How can we affect it?
• - We have tremendous new possibilities

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Ammonia synthesisN23H2? 2NH3
Ozaki and Aika, Catalysis 1 (Anderson and
Boudart, Ed.)
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Ammonia synthesis over Ru
Ru(0001)
step
Logadottir, Nørskov
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Steps do everything
Au decorates steps Hwang, Schroder, Gunther,
Behm, Phys. Rev. Lett. 67, 3279 (1991)  
Dahl, Logadottir, Egeberg, Larsen, Chorkendorff,
Törnqvist, Nørskov, Phys.Rev.Lett. 83, 1814
(1999)
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The Brønsted-Evans-Polanyi relation
Logatottir, Rod, Nørskov, Hammer, Dahl, Jacobsen,
J. Catal. 197, 229 (2001)
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Calculated ammonia synthesis rates400 C, 50 bar,
H2N231, 5 NH3
Logatottir, Rod, Nørskov, Hammer, Dahl, Jacobsen,
J. Catal. 197, 229 (2001)
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Interpolation in the periodic table
Jacobsen, Dahl, Clausen, Bahn, Logadottir,
Nørskov, JACS 123 (2001) 8404.
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Interpolation in the periodic table
Jacobsen, Dahl, Clausen, Bahn, Logadottir,
Nørskov, JACS 123 (2001) 8404.
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Measured ammonia synthesis rates 400 C, 50 bar,
H2N231
Jacobsen, Dahl, Clausen, Bahn, Logadottir,
Nørskov, JACS 123 (2001) 8404.
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Data driven methods

• High throughput screening
• Direct testing of many catalysts, fast,
  efficiently
• Data mining
• Correlating catalytic activity/selectivity/
  durability to descriptors that can be tabulated

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H. Toulhoat and P. Raybaud Workshop Catalysis
from First Principles Vienna 02/02
Using DFT calculations in the search of
prospective catalysts

• The object of the game
• Find sets of descriptors Dik of solid materials
  Mi , and a mathematical model F such that Aij
  being the Turn Over Frequency of Mi as catalyst
  for the reaction j at operationg conditions Cj
  one has
• Identify ranges of Dik that maximize F
• Screen Databases of Materials Properties before
  screening real materials
• Better if one descriptor is sufficient, but do
  not take it for granted
• Much better if F has a sound physical basis
• Adsorbate/substrate bond strengths should provide
  good descriptors according to the Sabatier
  principle

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H. Toulhoat and P. Raybaud Workshop Catalysis
from First Principles Vienna 02/02
Using DFT calculations in the search of
prospective catalysts
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H. Toulhoat and P. Raybaud Workshop Catalysis
from First Principles Vienna 02/02
Using DFT calculations in the search of
prospective catalysts

• E MC _at_ Fm-3m carbides is rather consistent with
  simple chemisorption models
• Onset of dissociative chemisorption as MC bond
  strength increases

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H. Toulhoat and P. Raybaud Workshop Catalysis
from First Principles Vienna 02/02
Using DFT calculations in the search of
prospective catalysts

• The experimental Alloying effects is correctly
  predicted

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Getting data/descriptors

• Structure (in situ)
• Spectroscopy (in situ)
• Surface thermochemistry
• Calculations
• There is a large need for systematic data
• - and for good descriptors

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Structure-activity Correlation Hydrodesulfurizatio
n of thiophene
Topsøe, Clausen, Massoth Hydrotreating Catalysis,
Science and Technology (Anderson and Boudart
(Eds.), Springer (1996).
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Descriptors from spectroscopy
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Single crystal microcalorimerty
Larsen, Starr, Campbell, Chem.Thermodyn. 33, 333
(2001) Brown, Kose, King, Chem. Rev. 98, 797
(1998).
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Descriptors from DFT
Correlation between adsorption energies and
activation barriers and the d-band center
Mavrikakis , Hammer, Nørskov Phys. Rev. Lett. 81,
2819 (1998)
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CO tolerance of Pt alloy anodes for PEM fuel
cells
Pt
M
S. Gottesfeld et al., J. Electrochem. Soc. 148
(2001) A11.
   Christoffersen, Liu, Ruban, Skriver, Nørskov,
J.Catal. 199, 123 (2001)
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How can the d-band center be changed?
Calculated d band shifts
Overlayer
Host
Ruban, Hammer, Stoltze, Skriver, Nørskov,
J.Mol.Catal. A 115, 421 (1997)
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Methane activation
Transition state for CH4 dissociation on Ni(211)
b
Bengaard, Rostrup-Nielsen, Nørskov
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Methane activation on Ni/Ru
Egeberg, Chorkendorff, Catal. Lett. 77, 207
(2001)
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Lessons from biology

• Catalysis at ambient temperature and pressure
• Extreme selectivity
• Direct coupling of energy into the important
  reaction coordinate (non-thermal catalysis)

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Nitrogenase
nitrogenase
ATP
complex formation
Fe protein

4Fe-4S cluster
MoFe protein
P-cluster
nucleotide replacement
ATP cleavage electron transfer
FeMo cofactor
Fe protein
reduction

complex dissociation
Burgess, Lowe, Chem. Rev. 96, 2983
(1996) Schindelin, Kisker, Schlessman, Howard,
Rees, Nature 387, 370 (1997)
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N2 hydrogenation on FeMoco
Rod, Nørskov JACS 122, 12751 (2000)
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The Fe Protein cycle
E
MoFe protein
Fe protein
ATP
1)
4Fe-4S cluster
FeMoco
P-cluster
2)
E
3)
ADP
E
4)
See also Spee, Arendsen, Wassnik, Marrit, Hagen,
Haaker, FEBS Lett. 432, 55 (1998)
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Comparing the FeMoco and Ru(0001)
Rod, Logadottir, Nørskov J.Chem.Phys.
112, 5343 (2000)
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Status

• Well developed basic understanding
  theory-experiment
• Beginning to be able to use it directly in
  catalyst design
• Some activity-descriptor correlations
• Host of new in situ methods for catalyst
  characterization
• New very powerful screening methods
• We have a starting point which is radically
  different from the situation 5 or 10 years ago!

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Moving forward

• More basic understanding theory-experiment
• Integration of the conceptual framework for
  heterogeneous, homogeneous and enzyme catalysis
• More systematic data (descriptors)
• Better synthesis methods
• Better coupling of catalyst design and process
  engineering
• INTEGRATION

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Promoting development
An integrated approach
Experiments, models
Synthesis testing characterization
Theory